Rock layers and Earth's history

Question 1

Which explanation best describes how scientists use evidence from rock strata to organize the geologic time scale for Earth’s 4.6‑billion‑year history?

Accepted Answer

By analyzing the sequence of rock layers and the fossils they contain, scientists identify major changes in Earth’s history and, using radiometric dates where available, divide the 4.6‑billion‑year record into eons, eras, periods, and epochs.

Answer

Researchers base the divisions of the time scale only on the appearance of dinosaur fossils, placing all other organisms into the same intervals.

Answer

Scientists measure the thickness of each rock layer and assign a fixed number of years to each centimeter, creating a time scale based solely on layer thickness.

Answer

The geologic time scale is organized according to the dominant color of each rock stratum, because darker rocks are always older than lighter ones.

Question 2

Which statement best explains how scientists use evidence from rock strata to organize Earth’s 4.6‑billion‑year history on the geologic time scale?

Accepted Answer

By examining the sequence and characteristics of rock layers, scientists arrange Earth’s 4.6‑billion‑year history into eons, eras, periods, and epochs.

Answer

Scientists base the geologic time scale solely on the absolute ages of rocks obtained from radiometric dating, without using their order.

Answer

Geologic time divisions are determined only by the types of fossils present, ignoring the surrounding rock layers.

Answer

The time scale is created by grouping rocks according to their color and mineral composition, regardless of their position in the strata.

Question 3

The table below shows where the fossil of the extinct plant Glossopteris has been discovered. | Continent | Glossopteris fossil found? | |-------------|---------------------------| | South America | Yes | | Africa | Yes | | Antarctica | Yes | | Europe | No | | Asia | No | Which statement best supports the idea that continents have moved relative to each other over geologic time?

Accepted Answer

The same fossil is found on continents that are now separated by oceans, indicating those continents were once joined.

Answer

The fossil appears only on landmasses that are currently adjacent, indicating those continents have never moved.

Answer

The fossil is found only on continents in the Southern Hemisphere, showing that climate differences caused its distribution.

Answer

The fossil is absent from Europe and Asia, proving those continents have always been separate from the others.

Try three questions

Which explanation best describes how scientists use evidence from rock strata to organize the geologic time scale for Earth’s 4.6‑billion‑year history?

Which statement best explains how scientists use evidence from rock strata to organize Earth’s 4.6‑billion‑year history on the geologic time scale?

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